The mammalian olfactory system has a tremendous capability to discriminate thousands of different odor molecules. Recent advances in molecular biology and functional imaging have established that odor information is encoded as spatial patterns of activated glomeruli distributed on the olfactory bulb surface. How these glomerular coding patterns are transformed within the olfactory bulb circuits is critical to odor discrimination and recognition, but remains to be understood. As a unique feature of olfactory bulb neuronal circuits, most of the cell-cell communication is mediated by synapses and gap junctions made between dendrites of principal mitral/tufted cell and local interneurons. Our previous research has established how signals encoding odor information are transmitted and regulated dynamically along the mitral cell primary and secondary dendrites. The aim of this renewal application is to continue this line of research by combining patch-clamp recording, two-photon calcium imaging and green fluorescence protein-targeted transgenic/knock-in mice to analyze how the bulbar neurons interact with each other at a level of circuits to process glomerulus-specific odor information. Specifically, we will test three major hypotheses. First, one important function ofperiglomerular cells is to orchestrate the glomerulus-specific firing synchrony through both dendritic synaptic transmission and electrical coupling in the glomerulus. Second, neuronal activities within different glomeruli can also achieve temporary synchrony, and both periglomerular and granule cells play a important role. Third, signal transmission in granule cell dendrites and spines has a spatio-temporal dynamics that can mediate the coupling and uncoupling of mitral cells from different glomeruli as in response to different odorants. These experiments are in line with our long-term objective to obtain critical information on the functional principles of olfactory bulb dendritic circuits and how these principles are involved in odor signal processing and discrimination. The progress toward this objective will yield novel insights into how the olfactory system can recognize thousands of different odors, and into the neural basis of smell-related disorders. [unreadable] [unreadable]